Shiites in a Pakistani city hit by a brutal terror attack have refused to bury their dead in protest, demanding that the government do more to protect them.

The minority Muslim sect has been targeted by a barrage of bombings and shootings.

The bombings yesterday in Quetta were the worst in a series of attacks across Pakistan that killed 120 people. It appeared to be the country's deadliest single day of violence in five years.

Most of the dead were Shiites killed in twin bombings at a billiards hall - a frightening reminder that Sunni extremists are increasingly targeting them.

Members of the beleaguered Shiite community in Quetta laid about 50 of their dead out in the street today, saying they would not bury them until the government improves security in the area. Young Shiite men also set tyres on fire and blocked a nearby road in protest.

"We want safety for our all sects, and all security measures should be taken for our safety, said Fida Hussain, a relative of one of the victims. "We will not bury them until the government fulfils all our demands."

The strike was the worst of three deadly bombings targeting Shiites and soldiers in Quetta, capital of the volatile Baluchistan province, and worshippers at a Sunni mosque in the north-west on the same day.

Five people who were wounded in the twin bombings at the billiards hall last night died of their wounds overnight, said police, putting the death toll from that attack at 86.

The billiards hall bombing, in a Shiite area of the city, started with a suicide attack followed by a car bomb minutes later. Militants often use such staggered bombings to maximise the body count by targeting rescuers and others who rush to the scene.

Today Shiite volunteers erected tents to keep bystanders away from the severely-damaged building, where the pool hall once occupied the basement.

Nearby resident Jan Ali described it as a neighbourhood gathering spot where young and old often waited in line to play on its six tables. He rushed to the scene night after the blast.

"It was a scene like hell on earth," said Ali. "Rescue people were carrying out dead and injured, people bleeding and crying, and rushing them toward ambulances. I have never seen such a horrifying situation in my life."

Pakistan's minority Shiite Muslims have increasingly been targeted by radical Sunnis who consider them heretics. Lashkar-e-Jhangvi, a Sunni militant group with strong ties to the Pakistani Taliban, claimed responsibility for yesterday's attack.

Last year was the bloodiest year for Pakistan's Shiite community in living memory, said Human Rights Watch. More than 400 Shiites were killed in targeted attacks in 2012; over 120 of them died in Baluchistan.

In the other incident in Quetta, a bomb hidden in a bag went off near a vehicle carrying paramilitary soldiers elsewhere in the city, killing 12 people and wounding more than 40 others.

The United Baluch Army, a separatist group, claimed responsibility for the attack.

Pakistan has faced a violent insurgency in Baluchistan for years from nationalists who demand greater autonomy, and a larger share of the country's natural resources.

The third blast Thursday targeted a mosque in the north-western Pakistani city of Mingora, killing 22 people and wounding more than 70.